[Test Coverage] container-startup-diagnostics.ts coverage

[github-actions]

Improves test coverage for src/container-startup-diagnostics.ts from ~65% to ~98%.

What's covered

New tests in src/container-startup-diagnostics-coverage.test.ts:

didContainerFailStartup

• docker inspect exits non-zero → returns false
• docker inspect throws → returns false
• Inspect output shows exited status → true
• Inspect output shows unhealthy health → true

logContainerLogsToStderr

• docker logs exits non-zero → no output logged
• docker logs succeeds with empty output → no output logged
• docker logs throws → handled gracefully

detectDnsResolutionFailure

• docker logs exits non-zero → null
• EAI_AGAIN pattern in stdout → hostname returned
• ENOTFOUND pattern in stderr → hostname returned
• No DNS pattern → null
• Throws → null

reportBlockedDomains

• Non-standard port on allowlisted domain → portIssues classification + fix suggestion (lines 161-162, 181)
• Wildcard *.domain.com matching with non-standard port → port issue (exercises lines 139-141)
• Protocol mismatch path
• Else branch (allowed domain, standard port)

handleHealthcheckError

• No denials found → rethrows original error
• Error message doesn't match → rethrows without calling checkSquidLogs
• Denials found → user-friendly domain error

Generated by Test Coverage Improver · 105.5 AIC · ⊞ 6.2K · ◷